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A (11)C molecular production/separation system (CMPS) has been developed as part of an isotope separation on line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive (11)C ion beams. In the ISOL system, (11)CH4 molecules will be produced by proton irradiation and separated from residual air impurities and impurities produced during the irradiation. The CMPS includes two cryogenic traps to separate specific molecules selectively from impurities by using vapor pressure differences among the molecular species. To investigate the fundamental performance of the CMPS, we performed separation experiments with non-radioactive (12)CH4 gases, which can simulate the chemical characteristics of (11)CH4 gases. We investigated the separation of CH4 molecules from impurities, which will be present as residual gases and are expected to be difficult to separate because the vapor pressure of air molecules is close to that of CH4. We determined the collection/separation efficiencies of the CMPS for various amounts of air impurities and found desirable operating conditions for the CMPS to be used as a molecular separation device in our ISOL system.

The Electron String type of Ion Sources (ESIS) was developed, constructed and tested first in the Joint Institute for NuclearResearch. 1 These ion sources can be the appropriate sources for production of pulsed C 4+ and C 6+ ion beams which can be used for cancer therapy accelerators. In fact the test ESIS Krion-6T already now at the solenoid magnetic field only 4.6 T provides more than 10 10 C 4+ ions per pulse and about 5·10 9 C 6+ ions per pulse. Such ion sources could be suitable for application at synchrotrons. It was also found, that Krion-6T can provide more than 10 11 C 6+ ions per second at 100 Hz repetition rate, and the repetition rate can be increased at the same or larger ion output per second. This makes ESIS applicable at cyclotrons as well. As for production of 11 C radioactive ion beams ESIS can be the most economic kind of ion source. To proof that the special cryogenic cell for pulse injection of gaseous species into electron string was successfully tested using the ESIS Krion-2M. 2

Electron beam ion sources (EBISs) provide the highest charge states of ion produced, high pulse ion currents, and a good emittance of an ion beam but an average ion current usually less than that for other sources of highly charged ions, for example, electron cyclotron resonance. The reason for that is an unusually small volume of electron–ion interaction, which is limited by the acceptable length of the source and by the electron beam perveance. To overcome the last limit while conserving all the advantages of the EBIS mentioned, the general idea of a tubular electron beam ion source (TEBIS) with an off-axis ion extraction is proposed. Construction of a TEBIS and its use in the normal or in the reflex mode of operation could increase an EBIS ion output 100–1000 times. The configuration of TEBIS and the current status of its development is described.

Electron String Ion Source (ESIS) Krion-2 (JINR, Dubna) was used for basic and applied research in various aspects of multiply charged heavy ions production. Energy recuperation mode in ESIS has been proofed first and used for production of highly charged ions 84Kr28+÷84Kr32+, 124Xe40÷124Xe44 and Au51+÷ Au54+. Krion-2 ESIS was mounted on high voltage (HV) platform of LU-20 Linac and used as an injector of highly charged ions during Nuclotron run N° 41. Krion-2 ESIS has produced 3.0·107 124Xe42+ ions per pulse of 7 μs duration. This ion beam was injected into LU-20 and Nuclotron, accelerated up to energy of 186 GeV and the extracted Xe beam was used for physics experiments. Electron String Ion Source Krion-2 demonstrated the high reliability and stability running during 30 days on HV platform. We believe that it is due to an extremely low electron beam power, provided by using the electron string mode of operation: 50 W pulse power and about 10 W average power. Other possible application of ESIS could be its use in injection complexes of synchrotrons and cyclotrons for cancer therapy. Slow and fast extraction of C4+ and C6+ beams from Krion-2 ESIS were preliminary studied towards ESIS optimization for medical accelerators requirements.

The most recent experimental information on electron string phenomenon, such as two step transition to electron string state, stability of e-strings in condition of electron energy recuperation, are described. The new technology developments of electron string ion sources (ESIS) include pulse injection of gaseous species in e-string and its efficient conversion to ion beams, slow ion extraction, ion-ion cooling of heavy ions with CH(4) coolant, and a progress in the construction of the new Joint Institute for Nuclear Research ESIS with 6 T solenoid are briefly considered.

The reflex mode of EBIS operation in certain conditions (a special construction of electron gun and electron reflector, a precise axial symmetry of solenoid with a strong magnetic field, a sufficient injected electron current at a certain energy which provide a sufficient density of accumulated electrons in EBIS drift space) leads to formation of the so-called electron string state of a pure one component electron plasma. It was shown experimentally, that electron strings are stable in a broad range of operational conditions to be used for production of highly charged ions in electron string ion sources (ESIS) similarly to streaming electron beams in EBIS. The EBIS “Krion-2” in the string mode of operation, by means of which electron string formation was first observed and majority of experimental information on its features has been obtained, was recently used as the source of highly charged ions on the Nuclotron accelerator facility. During two runs in June 2002 and June 2003 N6+, N7+, Ar16+ and Fe24+ ions of 300, 350, 200, and 150 μA pulse current, respectively, produced by this source were accelerated to relativistic energies and used in several experiments. During the runs the source situated on the high voltage platform of the LINAC preinjector worked mostly in an automatic mode of operation and showed high stability and reliability.